The present invention relates to a vacuum ejector for producing vacuums in industrial processes. More specifically, the invention relates to a multi-stage vacuum ejector in which the ejector stages are arranged in series and/or in parallel.
A multi-stage ejector having a plurality of ejector stages arranged in series and/or in parallel has long been known.
Typical of a multi-stage ejector is that it comprises an ejector housing, comprising two or more ejector stages, also termed ejector units, axially arranged one after the other in series. In each of the ejector units there is arranged a compressed air duct comprising an ejector nozzle for producing the vacuum flow of the ejector and a vacuum duct for said vacuum flow. The ejector units are separated from one another via transverse partition walls disposed in the ejector housing.
Compressed air is fed to the multi-stage ejector via a hose coupling or pipe coupling disposed in the first ejector unit of the multi-stage ejector. After having passed through the first ejector unit, the compressed air is forwarded at high velocity into a second ejector unit and thereafter, possibly, onward to a third and fourth ejector unit. In the spaces between the ejector units, between the outlet of an ejector nozzle and the inlet of a following ejector nozzle is formed an underpressure, also termed a vacuum flow, the size of which is determined by factors such as incoming compressed air, the number of ejector units, the distance between the nozzles of the ejector units, and the configuration of the nozzles.
In GB 2262135A, FIGS. 1 and 2, is shown a multi-stage ejector in an ejector housing, comprising axially arranged ejector units separated from one another via transverse dividing planes disposed in the ejector housing, wherein the dividing planes comprise feed-throughs for compressed air ducts and vacuum ducts, in which the ejector nozzles and nonreturn valves, respectively, are mounted.
U.S. Pat. No. 4,696,625A, FIG. 2, shows a multi-stage ejector similar to that in GB 2262135A. The multi-stage ejector according to U.S. Pat. No. 4,696,625A, FIG. 2, differs by virtue of the fact that the ejector housing also comprises a longitudinal plane in which the vacuum feed-throughs with nonreturn valves are disposed.
Various ways of mounting ejector nozzles in the compressed air feed-throughs have been proposed, for example various types of fastening joints such as glue joints, screw joints, threaded joints or shrink joints.
A problem with said multi-stage ejectors is their configuration with many separate parts which have to be mounted, transverse and horizontal planes, separate ejector nozzles, etc., which implies an increased risk of malfunction in the ejector. A large number of parts also implies that the risk of error in the production of the ejector is high, resulting in a high rejection rate.
In the light of the above, there is a need for a simple multi-stage ejector having few component parts, which has high reliability and which is cheap and easy to produce.
It is desirable to provide a simplified multi-stage ejector having few component parts, having high reliability, and which is easy and cheap to produce.
It is also desirable to provide a multi-stage ejector which can be easily miniaturized for use within, for example, microelectromechanical systems (MEMS).
Thus, according to aspects of the present invention, a multi-stage ejector for producing a vacuum flow in an industrial process has been provided, comprising at least two ejector units axially arranged at a predefined distance apart in an ejector housing, wherein each of the at least two ejector units comprises at least two parallelly arranged hollow feed-throughs having inlet and outlet nozzles for a compressed air flow and at least one hollow feed-through for the vacuum flow.
Characteristic of the multi-stage ejector is that each of the at least two ejector units with the hollow feed-throughs for compressed air having inlet and outlet nozzles for a compressed air flow and at least one hollow feed-through for the vacuum flow.
According to further aspects of the multi-stage ejector:
the ejector units are positionable in the ejector housing, via longitudinal grooves disposed on the outer side of the ejector units and via corresponding longitudinal guide rails disposed on the inner side of the ejector housing,                the ejector units are lockable via spring-pretensioned guide lugs on the inner side of the ejector housing and via corresponding recesses on the outer side of the ejector units,        the ejector housing is configured as a cylinder,        the first ejector unit and the third ejector unit comprise a sleeve coupling for connection to incoming and outgoing compressed air respectively, wherein the sleeve coupling comprises an outer sleeve, in which is mounted an inner sleeve, comprising a mounting seat for possible mounting of a nonreturn valve and a filter,        the sleeve coupling comprises transverse spring-loaded locking pins for locking the sleeve coupling to the respective ejector unit.        
The invention, according to aspects thereof, implies a number of advantages and effects, the most important being; simple design with few parts, with high reliability, which is easy to produce and fault-localize.
The invention, according to aspects thereof, also enables substantial miniaturization, for application to, for example, MEMS.
The invention, according to aspects thereof, also implies a simplified production process resulting in large cost benefits.
The invention, according to aspects thereof, has been defined in the following patent claims and shall now be described in somewhat greater detail in connection with the appended figures.